Loss of genetic diversity as a signature of apricot domestication and diffusion into the Mediterranean Basin

ABSTRACT: BACKGROUND: Domestication generally implies a loss of diversity in crop species relative to their wild ancestors because of genetic drift through bottleneck effects. Compared to native Mediterranean fruit species like olive and grape, the loss of genetic diversity is expected to be more substantial for fruit species introduced into Mediterranean areas such as apricot (Prunus armeniaca L.), which was probably primarily domesticated in China. By comparing genetic diversity among regional apricot gene pools in several Mediterranean areas, we investigated the loss of genetic diversity associated with apricot selection and diffusion into the Mediterranean Basin. RESULTS: According to the geographic origin of apricots and using Bayesian clustering of genotypes, Mediterranean apricot (207 genotypes) was structured into three main gene pools: 'Irano-Caucasian', 'North Mediterranean Basin' and 'South Mediterranean Basin'. Among the 25 microsatellite markers used, only one displayed deviations from the frequencies expected under neutrality. Similar genetic diversity parameters were obtained within each of the three main clusters using both all SSR loci and only 24 SSR loci based on the assumption of neutrality. A significant loss of genetic diversity, as assessed by the allelic richness and private allelic richness, was revealed from the 'Irano-Caucasian' gene pool, considered as a secondary centre of diversification, to the northern and southwestern Mediterranean Basin. A substantial proportion of shared alleles was specifically detected when comparing gene pools from the 'North Mediterranean Basin' and 'South Mediterranean Basin' to the secondary centre of diversification. CONCLUSIONS: A marked domestication bottleneck was detected with microsatellite markers in the Mediterranean apricot material, depicting a global image of two diffusion routes from the 'Irano-Caucasian' gene pool: North Mediterranean and Southwest Mediterranean. This study generated genetic insight that will be useful for management of Mediterranean apricot germplasm as well as genetic selection programs related to adaptive traits.     

Mise en évidence par charophytes et ostracodes de l’âge Paléocène des dépôts discordants sur les rides anticlinales de la région d’Imilchil (Haut Atlas,Maroc) : conséquences paléogéographiques et structurales

New sedimentological and biostratigraphical data have been obtained from unconformable series (Tasraft Formation) on some intruded anticlines located in the Central High Atlas of Morocco. Our results lead us to contest the previous Middle Jurassic to Middle Cretaceous ages only based on lithostratigraphic similarities. The Tasraft Formation proves to be a syntectonic series characterized by detritic fluvial sediments followed by lacustrine and lagoonal-marine limestones. Ostracods and charophytes found in different levels of the unconformable series indicate Thanetian ages. According to these new stratigraphical data, we can conclude that the main structures of the axial part of the High Atlas (folds, cleavage and exhumation of gabbroic bodies) were settled before the Late Paleocene. Moreover, the occurrence of Paleocene nonmarine beds in the axis of the High Atlas Belt implicates to modify the paleogeographic boundaries of the Atlantic transgressions in the beginning of the Tertiary.     

Use of cheese whey to enhance <Emphasis Type="Italic">Geotrichum candidum</Emphasis> biomass production in olive mill wastewater

Geotrichum candidum is a yeast-like filamentous fungus that has attracted industrial interest. The present work investigated G. candidum biomass production in agro-industrial wastewaters (olive mill wastewater (OMW) and cheese whey (CW)) as the only substrate. Different solid media (Sabouraud dextrose agar (SDA), CW, OMW, and OMW/CW mixtures in different proportions) were tested. OMW/CW mixtures proved to be suitable for optimal mycelia growth of G. candidum with a very high hyphae density. The highest fungal and expansion rate growth of 83 ± 1 mm and 12.4 day⁻¹, respectively, were obtained on a 20:80 mixture of OMW/CW, which was incubated for 7 days. This optimal mixture was used to study the biomass production and the OMW decolorization ability of G. candidum in the presence of CW in liquid medium. Liquid cultures were also conducted in OMW and CW separately. After 5 days of incubation, fungal biomass reached 9.26 g l⁻¹ in the OMW/CW mixture and only 2.83 g l⁻¹ in CW, while no biomass production was observed in OMW alone. OMW decolorization and dephenolization by G. candidum also improved in the presence of CW with a decolorization efficiency of 54.5% and a total phenolic reduction of 55.3%, compared with the control which yielded values of about 10% and 15%, respectively. These results suggested that OMW/CW—as the only substrate—could be used as a cost-effective medium to produce G. candidum biomass, without the need for water dilution or supplementation with other nutriments.     

Quantifying phylogenetically structured environmental variation

Comparative analysis methods control for the variation linked to phylogeny before attempting to correlate the remaining variation of a trait to present-day conditions (i.e., ecology and/or environment). A portion of the phylogenetic variation of the trait may be related to ecology, however; this portion is called "phylogenetic niche conservatism." We propose a method of variation partitioning that allows users to quantify this portion of the variation, called the "phylogenetically structured environmental variation." The new method is applied to published data to study, in a phylogenetic framework, the link between body mass and population density in 79 species of mammals. The results suggest that an important part of the variation of mammal body mass is related to the common influence of phylogeny and population density.     

A 7.1 kbp beta-myosin heavy chain promoter,efficient for green fluorescent protein expression,probably induces lethality when overexpressing a mutated transforming growth factor-beta type II receptor in transgenic mice

The roles of transforming growth factor-beta (TGF) in heart or skeletal muscle development and physiology are still the subject of controversies. Our aim was to block, in transgenic mice, the TGF signalling pathway by a dominant negative mutant of the TGF type II receptor fused to the enhanced green fluorescent protein (TRII-KR-EGFP) under the control of a 7.1 kbp mouse beta-myosin heavy chain (MHC) promoter to investigate the roles of TGF in the heart and slow skeletal muscles. First, we generated two transgenic lines overexpressing EGFP under the control of the 7.1 kbp MHC promoter. In embryos, EGFP was detectable as early as 7.5 days post coitum. In embryos, newborns and adults, EGFP was expressed mainly in the cardiac ventricles and in slow skeletal muscles. EGFP expression was intense in the bladder but weak in the intestines. In contrast to the endogenous MHC promoter, the activity of the 7.1 kbp MHC promoter in the transgene was not repressed after birth and remained high in adult transgenic mice. We obtained two founders with the transgene comprising the TRII-KR-EGFP sequence under the control of the 7.1 kbp MHC promoter. These founders were generated at a very low frequency and expressed barely detectable levels of TRII-KR-EGFP mRNA. Our failure to obtain transgenic lines overexpressing the dominant negative receptor suggests that the blocking of the TGF signalling pathway in the heart and slow skeletal muscles could be embryonically lethal. To conclude, the 7.1 kbp MHC promoter directs high levels of transgene expression in the cardiac ventricles and in slow skeletal muscles of the mouse. Analysis of the consequences of the blocking of the TGF signalling pathway in the heart will require the use of tissue specific means of conditional gene invalidation.     

Heterogeneity of NG2-expressing cells in the newborn mouse cerebellum

The function and origin of NG2+ cells in the adult brain are still controversial. A large amount of data is available which strongly indicates that adult NG2-expressing cells form a heterogeneous population, constituted by oligodendrocyte precursor cells (OPCs) and a fourth novel type of glial cells named the synantocytes. Whether these two populations derive from the progressive maturation of perinatal NG2+ OPCs or are generated as separate populations is not known. We used organotypic cultures of newborn mouse cerebellum depleted, by anti-mitotic drug treatment, of their NG2+ cells with perinatal features (high proliferating rate and high oligodendrocytic differentiation ability). In these cultures, despite the lack of myelin after 14 days in vitro, numerous NG2+ cells remained. We show that these BrdU-resistant cells were able to slowly divide, as adult NG2+ cells do. Although many of these cells expressed O4, only a very small fraction of them was further engaged in oligodendrocyte lineage, as they had an extremely poor capacity to generate myelin sheaths to the Purkinje cell axons. These results support the view that at least two distinct populations of NG2+ cells coexist in the cerebellum from birth: one with the young OPC characteristics, another with adult NG2+ cell characteristics. Thus, a fraction of adult NG2+ cells do not derive from the maturation of perinatal OPCs.     

Culture conditions of tannase production by Lactobacillus plantarum

Lactobacillus plantarum produced an extracellular tannase after 24 h growth on minimal medium of amino acids containing 2 g tannic acid l^–1. Enzyme production (6 U ml^–1) was optimal at 37 °C and pH 6 with 2 g glucose l^–1 and 7 g tannic acid l^–1 in absence of O₂.     

Electrical parameters in gallbladders of different species their contribution to the origin of the transmural potential difference

Summary Amphotericin B enhances Na⁺ conductance of the mucosal membrane of gallbladder epithelial cells and in such a way it modifies the brush border electromotive force. On this basis a method to measure cell and shunt resistances by comparing changes of the mucosal membrane potential (V _m ) and of the transmural p.d. (V _ms ) is developed. This method is applied in gallbladders of different vertebrate species (i.e. rabbit, guinea pig, goose, tortoise, toad, trout). The two tested mammals, rabbit and guinea pig, exhibited a lower shunting percentage (89–93%) than the nonmammals (96–97%), but this fact did not bring about a homogeneous positiveV _ms . This means that shunting percent contributes, but it is not the only source of differences inV _ms , in accordance with that reported by Gelarden and Rose (J. Membrane Biol. 19:37, 1974). Moreover, mammals exhibited a lower luminal resistance and a lower ratio between luminal and basolateral resistance than nonmammals. Possible causes of these differences are discussed.